knew. Figure of speech Metonymy (of Subj.) App-6. They knew before, but their knowledge now received. new meaning. Adam becomes "naked" by losing something of Elohim's glorious likeness. Romans 8:3 may refer to this.
fig leaves. The man-made covering contrasted, in the structure, with the God-made clothing (Genesis 3:21).
aprons. Hebrew word occurs only here.